Method for Automatically Generating Inverter Id for Multiple Interface Operation and Terminal Device for Distributed Resource Using the Same

The present invention relates to an automatic inverter ID generation method for multi-interface operation and a distributed power terminal device using the same, and more particularly, to an automatic inverter ID generation method for multi-interface operation and a distributed power terminal device using the same that are capable of automatically generating inverter IDs for multi-interface operation without collision of duplicate inverter Ids after verifying the validity of collected inverter Ids from smart inverters for performing DPI-based packet filtering in the distributed power terminal device.

Furthermore, the present invention claims the benefits of Korean Patent Application No. 10-2023-0154560 filed on Nov. 9, 2023, and the entire contents thereof are incorporated herein by reference.

Inverters are power conversion devices that convert direct current electricity generated by renewable energy sources into alternating current electricity, commonly referred to as “grid-connected inverter.” This means that the inverter has grid connection functionality added to the power conversion process, ensuring compliance with the grid code standards of all countries that utilize alternating current grid systems.

Distributed power inverters can be defined as power conversion devices that transform the maximum direct current power generated by renewable energy sources such as solar panels into alternating current power and deliver it to the power grid.

Power systems typically maintain stable voltage and frequency, but abnormal situations (e.g., sudden load surges, power supply drops), outages, or accident can cause voltage and frequency to deviate from normal ranges. In such scenarios, distributed power inverters must shut down within a specified time frame. Distributed power inverters must also have the ability to detect and disconnect from the grid upon encountering islanding, which is a phenomenon where an outage leads to the inverter supplying power to the grid independently.

Distributed power inverters must additionally possess the capability to generate reactive power as instructed by the utility company based on grid conditions and limit the total harmonic distortion of the output current to below 5% during grid-connected operation, Additionally, distributed power inverters provide the capability to notify power generation operator of renewable energy generation status, allowing for real-time monitoring anytime.

1 FIG. 1 FIG. is a diagram illustrating a central inverter and a string inverter. As shown in, inverters can be categorized into central (centralized) and string (distributed) inverters based on their internal structure. Firstly, central inverters have the advantage of a relatively simple structure with only one maximum power point tracking (MPPT) function, and they are typically used in megawatt-scale applications. Next, string inverters can be seen as simply a downsized version of central inverters. For example, a 1 MW central inverter can be replaced by ten 100 kW inverters, and in this case, the number of MPPTs increases as much as the number of string inverters used, which has the effect of increasing power generation, reducing internal power consumption, and having greater resilience to changes in the field environmental conditions. As a result, most inverters used in small-scale residential and commercial systems with capacities below 500 kWp are string inverters.

However, for string inverters, the interface of the existing low-voltage distributed power terminal unit (DER-LV-FRTU), typically installed at the interconnection point with distribution systems of less than 500 kWp (low voltage), needs to be modified to facilitate communication-based output control and monitoring. In other words, it is not easy for low-voltage distributed power terminal units to accommodate multiple string inverters, ranging from a minimum of two to potentially dozens, installed at a single site, through a single RS-485 interface. Therefore, low-voltage distributed power terminal units require multiple communication interfaces internally, and recent requirements have changed to accommodate the provision of multiple interfaces.

Meanwhile, existing firewall devices or web application firewall (WAF) devices provide deep packet inspection (DPI) functionality for power control protocols commonly used in power networks, such as Modbus and distributed network protocol (DNP).

In recent renewable energy plants utilizing multiple string inverters, the increasing number of string inverters connected may lead to conflicts or duplication of inverter IDs, thereby imposing constraints on the application of DPI algorithms for packet filtering, even though commercial products perform DPI-based packet filtering algorithm properly when each inverter has a unique and non-duplicated ID.

For this reason, low-voltage distributed power terminal units require multiple communication interfaces to manage multiple string inverters as output control resources. However, each of these communication interfaces assigns inverter IDs for each power generation site, leading to potential conflicts or duplications of IDs during the aggregation process within the low-voltage distributed power terminal unit.

The present invention aims to provide an automatic inverter ID generation method for multi-interface operation and a distributed power terminal device using the same that are capable of automatically generating inverter IDs for multi-interface operation without collision of duplicate inverter IDs after verifying the validity of collected inverter IDs from smart inverters for performing DPI-based packet filtering in the distributed power terminal device.

According to an embodiment of the present invention, an automatic inverter ID generation method for multi-interface operation may include receiving a response packet from each inverter in response to a request packet transmitted to request data measurement for all inverters, determining whether a collision state with the same inverter ID through multiple interfaces is detected upon receiving the response packet, and generating, upon detecting the collision state with the same inverter ID, a new inverter ID by collecting and distinguishing channel signals based on the physical communication connections and assigning inverter group information for each channel signal to the inverter ID.

The channel signals are channel signals per RS485 port and may be collected by confirming an indication signal information of the inverter communication status on a status indicator lamp of a terminal device.

The new inverter ID may be allocated as an 8-bit data value, with the first 2 bits assigned for the inverter group information as a group number and the remaining 6 bits assigned for the inverter ID.

The new inverter ID may be generated by combining the group number and the inverter ID using a SUBSTR(∥) function.

According to another embodiment, a distributed power terminal device may include at least one processor and a memory configured to store computer-readable instructions, wherein the instructions may be executed by the at least one processor for the distributed terminal device to receive a response packet from each inverter in response to a request packet transmitted to request data measurement for all inverters, determine whether a collision state with the same inverter ID through multiple interfaces is detected upon receiving the response packet, and generate, upon detecting the collision state with the same inverter ID, a new inverter ID by collecting and distinguishing channel signals based on the physical communication connections and assigning inverter group information for each channel signal to the inverter ID.

According to another embodiment, an automatic inverter ID generation method for multi-interface operation may include receiving a response packet from each inverter in response to a request packet transmitted to request data measurement for all inverters, determining whether a collision state with the same inverter ID through multiple interfaces is detected upon receiving the response packet, collecting and distinguishing, upon detecting the collision state with the same inverter ID, channel signals based on physical communication connections and performing logical operations between the channel signals and the inverter ID for conversion to a hash value through a hash function, and generating a new inverter ID by searching for a unique inverter ID in a hash table based on the hash value.

The performing of logical operations between the channel signals and the inverter ID may include replacing the channel signals with prime numbers and performing an exclusive OR (XOR) operation with the inverter ID.

The hash value may be converted into a value between 0 and 255.

According to another embodiment, a distributed power terminal device may include at least one processor and a memory configured to store computer-readable instructions, wherein the instructions may be executed by the at least one processor for the distributed terminal device to receive a response packet from each inverter in response to a request packet transmitted to request data measurement for all inverters, determine whether a collision state with the same inverter ID through multiple interfaces is detected upon receiving the response packet, and generate, upon detecting the collision state with the same inverter ID, a new inverter ID by collecting and distinguishing channel signals based on the physical communication connections and assigning inverter group information for each channel signal to the inverter ID.

The present invention is advantageous in terms of facilitating DPI-based packet filtering in distributed power terminal device by automatically generating inverter Ids without collisions of inverter Ids after verifying the validity of inverters IDs collected from smart inverters.

The present invention is also advantageous in terms of being implemented efficiently and lightweight within a low-specification processor in consideration of the system specifications of the low-voltage distributed power terminal unit (DER-LV-FRTU).

The present invention is also advantageous in terms of facilitating packet correlation analysis as the core process in the DPI algorithm without inverter ID information conflicts by initially verifying the validity of inverter ID information of multiple interfaces from smart inverters configured in multiple strings and automatically mapping this information.

Hereinafter, preferred embodiments of the present invention are described with reference to accompanying drawings. However, detailed descriptions of well-known functions or configurations will be omitted to avoid obscuring the subject matter of the present invention. It should be noted that the same reference numerals refer to the same components throughout the drawings.

The terms and words used in the following specification and claims should be interpreted not in a limited sense to their usual or dictionary meanings but in meanings and concepts that conform to the technical ideas of the present invention, based on the principle that the inventor can appropriately define the terms to best describe their invention.

Therefore, the embodiments described in this specification and configurations depicted in the drawings represent only the preferred embodiments of the present invention and do not fully embody all the technical ideas of the present invention, so it should be understood at the time of this application that there may be various equivalent elements and alternative embodiments that can replace them.

In the attached drawings, certain components may be exaggerated, omitted, or depicted schematically, and the sizes of individual components may not be proportional to their actual sizes. The present invention is not limited by the relative sizes or spacing shown in the attached drawings.

Also, when a part is said to “comprise” a certain component, this means that other components may be further included instead of excluding other components unless specifically stated otherwise. Additionally, when one part is “connected” to another part, it includes not only being “directly connected” but also being “electrically connected” through intermediate components.

As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprising” or “having” indicate the presence of the features, numbers, steps, operations, components, parts, or combinations thereof as listed in the specification, without excluding the presence or possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

In addition, the term “module” used in the specification means a software or hardware component such as a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks. However, the term “module” is not limited to software or hardware. A “module” may be configured to reside on addressable storage media and may be configured to execute one or more processors. Thus, a module may include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionalities of the components and modules may be combined into fewer components and modules or further separated into more components and modules.

The embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings to facilitate implementation by those skilled in the art within the relevant technical field. However, the present invention can be embodied in various forms, and is not limited to the embodiments described herein. In order to clearly describe the present invention, parts irrelevant to the description may be omitted in the drawings, and similar reference numerals may be used for similar components throughout the specification.

Hereinafter, preferred embodiments of the present invention are described with reference to the accompanying drawings.

2 FIG. 3 FIG. 2 FIG. is a diagram illustrating a distributed power terminal device according to an embodiment of the present invention, andis a diagram illustrating the multi-interface structure of a distributed power terminal device in.

2 3 FIGS.and 100 As shown in, the distributed power terminal deviceaccording to an embodiment of the present invention, installed at the interconnection point with low-voltage distribution systems of less than 500 kWp for communication with string inverters for output control and monitoring, expands physical ports to accommodate increasing numbers of string inverters and provides an RS485 multi-interface environment.

100 110 110 The distributed power terminal deviceincludes an RS485 connectorfor multiple interfaces for communication with string inverters. The RS485 connectoris composed of three channels of serial ports for communication with multiple inverters.

100 121 122 131 141 151 152 153 154 161 162 163 In addition, the distributed power terminal deviceincludes RS232 connectorsandfor main device communication and backup, an RJ-45 connectorfor Ethernet communication, a USB connectorfor firmware upgrades, a current measurement connectorfor electrical status verification, a voltage measurement connector, a status input connector, a control output connector, a battery connectorfor external device connection, a dedicated modem connector, and a power input connector.

100 110 100 100 The distributed power terminal deviceis connected to inverters from different renewable energy operators through the RS485 connector. In this case, the distributed power terminal deviceconnects to the serial port using the inverter ID numbers ranging from 01 to 99, designated for string inverters within the power generation site. Since inverter ID numbers are sequentially assigned and preset, they cannot be arbitrarily changed at the level of the distributed power terminal deviceeven in the event of conflicts between power generation operators. Due to the fixed settings of inverter ID numbers established during the installation phase, even if conflicts arise after on-site construction is completed, changing the inverter IDs arbitrarily without the consent of the power generation operator is difficult, and inspecting all communication specifications within the inverter device makes it impractical to change the IDs in practice.

100 Therefore, the distributed power terminal deviceadjusts the numbers between conflicting inverter IDs to distinguish each inverter for output control and on-site status monitoring, and performs a bulk conversion mapping of the inverter IDs to be used in internal operations after distinguishing the physical communication connections.

4 7 FIGS.to 4 FIG. 5 FIG. 6 FIG. 7 FIG. 5 FIG. A detailed description thereof is provided with reference to.is a flowchart illustrating the process of DPI-based packet filtering through automatic inverter ID generation according to an embodiment of the present invention,is a flowchart illustrating an automatic inverter ID generation method for multi-interface operation according to an embodiment of the present invention,is a diagram illustrating the front view of a distributed power terminal device, andis a diagram illustrating an inverter ID incorporating the inverter group number in.

100 The distributed power terminal deviceincludes at least one processor and memory for storing computer-readable instructions, and the computer-readable instructions stored in the memory are executed by the at least one processor to carry out the method for automatically generating inverter IDs for multi-interface operation according to embodiments of the present invention.

4 FIG. 100 As shown in, the distributed power terminal deviceperforms deep packet inspection (DPI)-based packet filtering analysis for packets incoming to the utility company control network because the compatibility and reliability of inverter IDs from customer equipment (renewable energy generation operator's equipment) cannot be guaranteed.

100 201 Firstly, the distributed power terminal deviceperforms inverter ID validity verification at step Sto determine whether conflicting inverter IDs occur to distinguish device information and measured values of each inverter for on-site status monitoring.

100 202 100 When conflicting inverter IDs occur, the distributed power terminal deviceproceeds with signal processing differentiation based on physical communication connections and converts the inverter IDs of the respective inverters accordingly at step S. During this process, the distributed power terminal deviceperforms bulk conversion mapping of the inverter IDs to be used in internal operations for DPI-based packet filtering inspections.

100 100 203 204 100 205 206 Subsequently, the distributed power terminal deviceperforms comprehensive packet inspection functionality. That is, the distributed power terminal devicefirst analyzes the structure of each communication packet at step Sand verify the validity of measurement/metering information at step S. Then, the distributed power terminal deviceperforms packet filtering inspections by defining a simple ruleset at step Sand defining a correlation ruleset between request/response packets at step S.

100 100 4 FIG. 5 FIG. Meanwhile, the distributed power terminal deviceuses the newly converted inverter ID scheme to confirm inverter information during the DPI-based packet filtering process described with reference to; however, in cases where further verification is required and communication with the inverter is necessary (for example, when installing a new inverter), it is necessary to manage mapping information to ensure inverter ID consistency during conversion back to original inverter IDs and performs bulk conversion mapping of inverter IDs for internal operations.illustrates the verification process of the distributed power terminal devicefor new inverter installations.

5 FIG. 100 301 302 As shown in, the distributed power terminal devicetransmits request packets (TX) in batch at one-minute intervals to request data measurements from all connected inverters at step Sand receives response packets (RX) containing sets of measured values for the power output of renewable power plants from each inverter at step S.

100 303 304 305 2 FIG. Upon receiving the response packets (RX) containing the same inverter ID value through the multiple interfaces, the distributed power terminal devicedetects the collision status of inverter IDs at step S, gathers and differentiate channel signals based on the physical communication channel connections (i.e., RS485 port-specific channel signals) at step S, and assigns channel signal-specific inverter group information to each existing inverter ID at step S. Here, the RS485 port constitutes a multi-interface and may be divided into three channels as described with reference to.

100 170 6 FIG. After detecting an inverter ID collision in response packets (RX), the distributed power terminal devicecollects channel signals from each RS485 port by checking the ‘inverter communication status (RS485)’ signal information on the status indicator lampas shown in.

Here, the ‘inverter communication status (RS485)’ lamp indicates the connection status and transmission/reception activity for each channel (i.e., RS485-1, RS485-2, and RS485-3) in red (on) or black (off). The number of each channel corresponds to the group information assigned to each inverter.

304 100 For example, upon detecting an inverter ID collision at step Swith the indication by the ‘inverter communication status (RS485)’ lamp turning red (on) for the receiving packet (RX) signal channels RS485-1 and RS485-3, the distributed power terminal deviceassigns inverter group information as group 01 and group 03 to each received packet, respectively.

100 306 307 308 Next, the distributed power terminal devicecollects the inverter ID from the response packet (RX) at step S, generates the inverter ID for the new inverter automatically at step S, and sets the new inverter ID within the terminal device and manage the consistency of the inverter ID to be used in internal operations at step S.

7 FIG. illustrates the process of automatically generating an inverter ID by incorporating additional group information (i.e., group numbers) extracted from channel signals of multiple interfaces.

100 100 6 FIG. As described above, the distributed power terminal devicemay identify and assign inverter group information without any additional electronic signal processing, utilizing the status indicator lamp signals on the front panel of the existing terminal devices for communication status indication purposes. That is, upon confirming the red (on) illumination of the receiving packet (RX) lamp for the RS485-N channel signal on the front panel of the terminal device as shown in, the distributed power terminal devicerecognizes this as a valid received packet and assigns additional information in the form of ‘group N’to each of these packets.

6 Specifically, the inverter ID is typically assigned as an 8-bit data value. Here, the first 2 bits are newly assigned as the ‘group number’, while the remaining 6 bits are used as the existing ‘inverter ID’. For this purpose, the ‘group number’ and ‘inverter ID’ are combined using the SUBSTR(∥) function. In other words, the inverter ID is used in the form of inverter ID=group number∥inverter ID. In this case, the maximum number of inverters that can be connected as a string to each RS485 port is 64 (6 bits, 2=64). However, there is a limitation that renewable energy sources newly installed as a string type exceeding the maximum number of inverters cannot be accommodated within the same RS485 serial port. However, as renewable energy operators are currently instructed to distribute and accommodate up to 99 inverters within 3 serial ports when deploying string-type inverters at installation sites, it is possible to utilize the system without exceeding the maximum inverter count per RS485 port by distributing 33 inverters to each RS485 port.

100 In this manner, the distributed power terminal devicecan automatically generate an inverter ID by combining inverter group information with the existing inverter ID.

100 8 9 FIGS.and Meanwhile, a description is provided of the process for the distributed power terminal deviceto automatically generate invert IDs according to another embodiment with reference to. In this embodiment, a probing technique that utilizes a hash function to identify available inverter IDs is employed.

8 FIG. 9 FIG. 8 FIG. 8 FIG. 5 FIG. 303 is a flowchart illustrating automatic inverter ID generation method for multi-interface operation according to another embodiment of the present invention, andis a diagram illustrating the resolution of hash collisions using a hash table in. In, stepis identical with that in, and thus the detailed explanation thereof is omitted.

5 FIG. In, a method was illustrated for automatically generating inverter IDs by combining additional group information (i.e., group numbers) extracted from channel signals of multiple interfaces.

8 9 FIGS.and 100 100 As shown in, the distributed power terminal deviceautonomously assigns and generates inverter IDs by adapting the probing technique based on a hash function. This makes it difficult for hackers to easily match and infer inverter IDs even when they gain root access to the distributed power terminal device.

100 The measurement/metering items collected from the inverter by the distributed power terminal devicemay include per-inverter ID, phase-specific voltage/current/active power/reactive power, three-phase average voltage/current/active power/reactive power, power factor, and frequency.

303 100 352 353 100 In detail, upon detecting an inverter ID collision through multiple physical interfaces at step S, the distributed power terminal devicecollects channel signal informations the channel signal information based on physical communication connections (i.e., channel signals per RS485 port) and the inverter ID of the received packet (RX) at step Sand performs simple logical operations between the collected information and inverter IDs at step S. That is, the distributed power terminal deviceperforms exclusive OR (XOR) operations between the inverter IDs and substitutes the channel signals from different physical RS485 interfaces with a very large number of prime numbers to provide unique hash values for multiple inverter IDs. This process employs the exclusive OR operation on bits, similar to cryptographic key generation, to automatically generate unique and collision-free inverter IDs for each device.

100 354 355 100 9 FIG. Afterwards, the distributed power terminal deviceapplies the result of the logical operations, which have been transformed into very large numbers, to a hash function to output a hash value at step Sand sets a new inverter ID using the hash value at step S. That is, the distributed power terminal deviceutilizes a hash function to convert multiple inverter IDs into a hash value between 0 and 255, and then searches the hash table with 256 rows for unique inverter IDs and map and set them as a new inverter IDs as shown in.

9 FIG. 1 100 1 2 3 1 100 1 1 6 1 2 1 1 3 2 In, the inverter ID ‘inverter’ is in a collision state. The distributed power terminal deviceperforms an exclusive OR operation between the channel signal information (channel signal, channel signal, and channel signal) and the inverter ID (inverter), then applies the result to a hash function to convert it into a hash value, and finally searches for a unique inverter ID within the 256-row of the hash table. Subsequently, the distributed power terminal devicesets the new inverter ID for the invertercorresponding to channel signalas ‘Inverter’, sets the new inverter ID for the invertercorresponding to channel signalas ‘inverter’, and sets the new inverter ID for the invertercorresponding to channel signalas ‘inverter’.

As such, embodiments of the present invention are capable of the management and operation of inverter IDs, allowing for the automatic generation of inverter IDs for multiple smart inverters without altering the device information on the inverter side, thereby facilitating the normal execution of DPI-based packet filtering processes.

Furthermore, embodiments of the present invention are capable of providing a preprocessing step for inverter ID refinement for DPI-based packet filtering algorithms, allowing the analysis of correlation between transmitted and received packets.

The method according to some embodiments may be implemented in the form of program instructions that can be executed by various computing means and recorded on computer-readable media. The computer-readable media may store program instructions, data files, data structures, or a combination thereof. The program instructions recorded on the media may be specifically designed and configured for the present invention or may be publicly known and available for use by computer software professionals. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program instructions, such as ROMs, RAMs, and flash memory. Examples of program instructions include machine code generated by compilers as well as high-level language code that can be executed by a computer using interpreters and similar tools.

While the above description focuses on the novel features of the present invention applicable to various embodiments, those skilled in the art will understand that various deletions, substitutions, and modifications may be made in the form and details of the devices and methods described above without departing from the scope of the present invention. Therefore, the scope of the present invention is defined by the appended claims rather than the foregoing description. Any modifications within the scope of equivalence of the patent claims are considered to be encompassed within the scope of the invention.